Abstract: The core of community building lies in the cultivation of community actors, and its outcomes are reflected in the optimization of the community's social network structure. To explore the internal mechanisms of community building, this study takes H Community in Shishi City, Fujian Province, as a case and employs Social Network Analysis (SNA), supplemented by process tracing and interview data. The study aims to identify different pathways of community building and their underlying mechanisms, and to link quantitative changes in network structure with qualitative evidence of these mechanisms. The findings show that community building has driven the social network of H Community from a single-center structure toward a multi-centered configuration, characterized by increased network density, decreased centralization, and a more diversified distribution of core nodes. Further analysis reveals three mechanisms through which community building optimizes network structures: initial mobilization through cultural arenas, the construction of mobilization pathways based on local social networks, and the institutionalized development of self-organized groups.